Rubber Composite Materials-Bound Rubber’s Structures And Properties:Insights From Molecular Dynamics Simulation Study

With the rapid development of science and technology, nanocomposites, nanocompounding techniques, elastomer-based(or Polymer-based) nanocomposites have been widely used in people’s daily life. And they are also intensively investigated in the scientific community. And bound rubber is one typical characteristics of elastomer-based(or Polyme-based) nanocomposites. Adopting molecular dynamics simulation plays a significantly important role in explaining the phenomenon in experiments. Based on this, there are three crucial sections of our work covered in this thesis.First, the conditions for forming chain bridges:By simulating polymer nanocomposites filled with small solvents through a typical coarse-grained model, we monitor the formation of bound rubber, which is composed of many chain bridges by being adsorbed onto neighboring nanoparticles (NPs). By examining the effects of the chain length and inter-particle distance on the number of "chain bridges", we observe that the two times of the root mean-square radius of gyration of polymer chains (2Rg) is the key parameter, and when the surface-to-surface distance between the two spherical NPs is smaller than 2Rg, the chain bridges begin to form, which is independent of the polymer-NPs interaction strength.Second, the forming mechanism ofbound rubber:By calculating those physical parameters such as the mean-square displacement (MSD), radial distribution function (RDF), the total interaction energy between polymer and solvents, polymer and nanoparticles(NPs), NPs and solvents, and the number of "chain bridges" formed between neighboring NPs, we have systematically studied the structure and dynamics of polymer nanocomposites filled with solvents. We adopted three methods to test the process of bound rubber’s formation mechanism. Eventually, we find that the volume fraction of nanoparticles plays an important role in the formation of bound rubber. As long as the volume fraction is abovea certain amount, bound rubber will be formed without other necessary factors.Third, the mechanical property of nanoparticle-polymer-solvent system:we also find that the added solvents deteriorate the mechanical property of polymer-NPs system by acting as plasticizers, which can be explained by the decrease of the chain orientation extent. Generally, this simulation work could provide some theoretical guidance for better understanding polymer-nanoparticle-solvent system.